As shown in Fig. 3F, anti‐Chi3L1 antibody significantly decreased the expression of cancer growth and migration‐associated proteins, such as PCNA, cyclin D1, cyclin E, Cdk2, Cdk4, Cdk5, MMP2 and MMP9 in A549 lung metastasis model tissues (Fig. 3F,G). This evidence concerns the gene MMP2 and cancer.